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BP: Fachverband Biologische Physik

BP 21: Membranes and Vesicles II

BP 21.5: Talk

Tuesday, April 1, 2014, 15:00–15:15, ZEU 250

Probing the influence of soluble domains on the diffusion of peripheral membrane proteins — •Gernot Guigas and Matthias Weiss — Experimental Physics I, University of Bayreuth, Bayreuth, Germany

Diffusion coefficients of membrane proteins are commonly assumed to be well predicted by the Saffman-Delbrück relation. The latter describes proteins as single membrane-spanning cylinders, i.e. effects of bulky extra-membrane domains and spatial protein interactions at crowded conditions are neglected. However, these quantities potentially play an important role for the survival of parasites of the trypanosome family in the bloodstream of mammals. To evade antibody recognition by the host's immune system, trypanosomes exchange their complete, very dense surface coat of bulky GPI-anchored glycoprotein VSG by a genetic variant within few minutes. Diffusion plays a crucial role for an efficient exchange of the dense VSG coat. We have used coarse-grained membrane simulations to study the diffusion properties of VSG and similar peripheral membrane proteins at crowded conditions. Both protein packing density and the size of the soluble domain have a strong influence on protein mobility. Diffusion coefficients are reduced by almost an order of magnitude when the VSG surface area fraction reaches physiological values of 30% and more. Enlarging the extra-membrane domain results in a similar reduction of VSG's diffusional mobility.